1,4-Butanediol (hereinafter, sometimes simply referred to as “1,4BG”) is known to be a very useful substance used as a raw material of various solvents or derivatives. Conventionally, a variety of methods for industrially producing 1,4BG have been developed and, for example, there are known a method of performing an acetoxylation reaction by using butadiene as a raw material and using the raw material butadiene, acetic acid and oxygen to obtain diacetoxybutene that is an intermediate, and hydrogenating and hydrolyzing the diacetoxybutene to produce 1,4BG (Patent Document 1), a method for obtaining a 1,4BG-containing crude hydrogenation product by using maleic acid, succinic acid, maleic anhydride and/or fumaric acid as raw materials and hydrogenating them (Patent Document 2), and a method for producing 1,4BG by hydrogenating butynediol that is obtained by using acetylene as a raw material and contacting it with an aqueous formaldehyde solution (Patent Document 3).
In such a process for producing 1,4BG, it is known that an unsaturated compound having a carbon number of 4 occurs as a byproduct. For example, in the production by an acetoxylation reaction of butadiene, 1,4-diacetoxy-2-butene, 1-acetoxy-4-hydroxy-2-butene, 1,4-dihydroxy-2-butene or the like occurs as a byproduct. Furthermore, in the case of the production method by hydrogenation of maleic acid or the like, gamma butyrolactone is produced. Also in the case of using acetylene as a raw material, 1,4-dihydroxy-2-butyne, 1,4-dihydroxy-2-butene or the like occurs as a byproduct. These unsaturated compounds may be separated directly by a distillation column, but the step for separation can be omitted by performing a hydrogenation reaction to convert those compounds into a different compound easily separable from 1,4BG and thereafter, separating the compound by distillation or the like or converting it into 1,4BG.
Various catalysts for use in such a hydrogenation reaction are present, and as regards the catalyst capable of suppressing reduction in the selectivity due to a byproduct at the hydrogenation, for example, Patent Document 4 has reported that the amount of byproduct butyl acetate can be reduced by performing hydrogenation of 1,4-diacetoxy-2-butene in the presence of an alkali metal or alkaline earth metal of acetic acid. Also, Patent Document 5 has reported that an effect of improving the reaction rate is obtained by allowing an amine to exist at the time of hydrogenating octadienols by a solid catalyst.